An Israeli official said on Sunday that the United States would notify Israel hours in advance of an attack on Syria.

While formally on the sidelines of the Syria crisis, Israel fears coming under reprisals from its northern foe should the United States launch strikes to punish Damascus for alleged use of chemical weaponry.

Asked how much advance notice Israel would get from its US ally about such attacks, the Israeli official, who was briefed on contacts with Washington, told Reuters: "Hours."

Israel plans to deploy anti-missile systems and troop reinforcements if President Barack Obama, who faces domestic resistance over the military intervention in Syria, gives the green light for US action.

Obama has asked Congress to approve strikes against Syrian President Bashar Assad's government in response to a chemical weapons attack on Aug. 21 that killed more than 1,400 Syrians.

Next week in Washington, hundreds of activists of the influential pro-Israel American Israel Public Affairs Committee will lobby Congress for military action in Syria.

At the weekly Israeli cabinet meeting on Sunday, Prime Minister Benjamin Netanyahu made no direct reference to the Syrian debate in the United States.

But Israeli officials have privately voiced concern US failure to attack Syria would embolden Iran, an ally of Damascus, in its defiance of international calls to curb a nuclear program which the West fears is aimed at developing nuclear arms.